Our Secret Night
by Killerchainsaw
Summary: 'Fate/Kaleid Liner Prisma Illya' oneshot about a secret night between Illya and Kuro. Rated M for mature content.
**Author's notes:**

 **I don't own 'Fate/Kaleid Liner Prisma Illya' or any of its characters, no copyright is intended.  
**

 _Italics - Means the person is thinking just so you know.  
_

 **Warning: This one-shot contains a yuri (girl x girl) pairing (as well as incest), don't like, don't read simple, otherwise enjoy. :D  
**

 **WARNING: This contains lemon ;P**

 **...**

"Mmm….so relaxing," Illya hummed to herself happily as she shuffled to sink herself lower into the warm bathtub.

Today had been like any other with studying hard for school, meeting up with her friends and going shopping with her Mother and 'little sister', also not forgetting a short Mana transfer, once the two young girls had returned home with their Mother for a delightful dinner before all heading to bed.

But all of that was now all over and she could finally relax in the bath all by herself, while the heavy rain poured down outside the window, as evening set in and Illya truly felt at peace for a few moments in time.

However Illya was sure that this wouldn't last as a certain dark-skinned girl with long pink hair would probably soon walk in to ruin the rare peace and quiet she was getting right now after a long day.

None the less Illya wanted this time she had to herself to be well spent, as she lay one leg over the other and folded her arms behind her head, resting her head on the end of the fairly small bathtub and slowly closing her eyes as she let out a long pleasant sigh of relief.

However sure enough the young girl's perfect moment of true peace was soon cut short, as she heard the slight 'creak' of the bathroom door opening and then closing, followed by light footsteps of bare feet walking across the cold tiled bathroom floor.

Illya slowly opened one eye and looked to her intruder, already knowing who it was without having to look at them. There she stood, completely naked and shivering a little at the cold getting to her, her long light-pink hair was flowing freely down her bare back, as her darkly-toned skin seemed a little lighter as the moonlight from the window, peeking in through the curtains mixed with the bright, blinding light of the bathroom light shone down on the girl, Illya's dear little sister.

"Hey Kuro, sorry I started without you, you were taking quite a while to get ready, so I decided to get in first and wait for you," Illya smiled to the other girl as Kuro stood there with her hands behind her back, and her bright eyes looking to the bath, rather than back to her sister.

"Its fine," Kuro shrugged her shoulders as her eyes were still focused more on the bath than anything else right now.

Illya sat patiently for a minute looking to Kuro with a questionable look as to why she hadn't gotten into the bath just yet, since this was strange, as the dark-skinned girl would normally just be happy to jump right in without a second thought.

Illya's head tilted to the side in a confused manner as she had now put her arms back down to rest at her sides, and her head had lifted off of the edge of the bathtub. Taking more notice as to why Kuro was hesitating so much, she had now noticed that the other girl was staring intently at the bath water, almost as if to be inspecting it using only her keen, bright eyes.

"Something the matter, why are you just standing there?" Illya asked nervously.

"The bath water smells funny, also it's pink," Kuro pointed out simply.

"Yeah don't worry, it's meant to be like that. You see I've been saving up my pocket money for a while now and I was finally able to buy this great brand of lotion, which can also be used as bubble bath. Just get in already it feels heavenly, trust me," Illya explained while Kuro seemed a little cautious at first but happily settled into the bath once Illya had moved her legs to make room for the two of them.

Kuro smiled as the warm water surrounded her cold body, she soon relaxed and lay her head back on the edge of the bathtub, "So is this…. 'Lotion' what you got so excited over in the store today?"

"Yeah, I had seen it advertised on T.V a little while ago and I really wanted to get it, and now I'm so glad that I had saved up my money in order to buy it," Illya now smiled again seeing that Kuro now seemed relaxed and back to her regular-self.

"At least you didn't waste it all on Anime and Manga, like you almost always do," Kuro wasn't wrong, but it's not like Illya would ever admit that, so instead she just glared to her slightly and mumbled something under her breath.

Illya frowned in confusion a little as Kuro seemed to be a little uncomfortable for some reason, as she shuffled slightly and hugged her knees upto her chest. Tucking a few locks of long hair behind her ear, and sighing heavily.

"What's up Kuro?" Illya asked, wondering why her sister's mood had suddenly changed, from relaxed, to on-edge in a matter of a few minutes.

"Nothing, it just feels a little like a 'Hot Spring', that's all," Kuro answered nervously.

"Yeah I guess it does kinda feel like that, but I'm sure it's just for effect," Illya smiled with a small nod to the other girl, _'Actually I think something like that was mentioned on the advert that I heard about this lotion from,'_ Illya thought for a moment.

"Hey Illya!"

"Yeah?" Illya was brought out of her thoughts as Kuro called to her, and she shook her head, looking back to Kuro again.

"Think fast!" Kuro smirked as she splashed the bath water into Illya's face.

Illya was too slow to move out of the way as she just closed her eyes, and let the pink bath water rain down onto her. She opened one eye and glared to Kuro slightly, but her expression softened as she heard the cheerful sound of Kuro's laughter.

"Wow, you've gotten a lot slower huh?" Kuro smirked again as she muffled her laugh with on one hand over her lips.

"Oh yeah? TAKE THIS!" Illya splashed Kuro back with a smile.

Kuro gave out a small squeal, followed by her cheerful laughter again as she shielded herself with one arm, while bath water showered down over her. And thus the two young girls began the childish splashing battle as they both laughed happily and soon soaked the bathroom floor.

At some point of the little 'Splashing battle' Illya was now on her knees, splashing Kuro over and over again, hoping to get the upper-hand on her little sister, however not really paying attention to where her legs were, she soon slipped and fell.

The splashing now had been halted as Illya quickly lifted herself up and got her balance back, looking to Kuro now, "Sorry Kuro, are you alright?" she asked with a worried expression as she checked Kuro's body over for any injures from her falling on top of her, as she rested her hands on either side of Kuro's legs.

"I'm fine, Illya don't worry," Kuro smiled as she chuckled slightly at her older sister's clumsiness.

"Are you sure because….." Illya paused slightly as she gazed into Kuro's bright eyes, and instantly started to get lost in them, _'Her face is so close to mine, I never noticed how weirdly coloured her eyes are before, mine are a dark shade of red, while her's are almost golden, kinda like a cat's really. Even though we're meant to be the same person, it's strange that we are so different from each other,'_ Illya sat on her hands and knees looking deep into Kuro's eyes, feeling paralysed at that moment in time.

"Hey while you're in this position, would you mind replenishing my Mana?"

That question caused Illya to be snapped right back to her senses as she shook her head quickly and composed herself, "But I already gave you some earlier when we came home from shopping with Mama, wasn't that enough?" Illya asked moving slightly away from Kuro, only really noticing now that she was leaning over Kuro, almost like she was pinning her to the edge of the bathtub.

"But I'm tired, and I feel really weak," Kuro stated in a whining tone as she looked to Illya with begging eyes.

"You probably just need to sleep for a bit," Illya rolled her eyes and turned away from Kuro slightly, blushing a little.

Illya was resisting, but Kuro knew exactly how to deal with her at times like this, "Fine, if you won't do it, I can just get Onii-chan to provide me with some, I'm sure he'll give me lots and lots," she smirked, already knowing that her words had gotten to Illya.

Illya froze when she heard their older brother being mentioned and immediately glared to Kuro again, while Kuro just happily smirked and stuck out her tongue to Illya.

"Fine I'll do it, but make it quick okay?" Illya blushed deeply as she reluctantly gave in without much more of a protest.

Kuro just nodded with a smile as she linked her arms around Illya's neck, and pulled her closer, closing her eyes a second later as Illya soon copied her and leaned into her more, trembling slightly as her lips brushed against Kuro's

' _I never can get used to this,'_ Illya sighed as she soon felt Kuro deepen the kiss and push her tongue into her sister's mouth. Slight moans and gasps could be heard from Illya's lips as Kuro's tongue played around with her's and within a few minutes she could feel Kuro sucking on her tongue, causing her to moan a little louder.

Illya could feel her breath running short as she moaned more and trembled slightly when she noticed that Kuro had started to press her bare knee in-between her legs, causing her to spread them a little.

' _N-no m-more, I c-can't…..her tongue….'_ Illya's mind was going blank as she was now at her limit and quickly broke the kiss, panting heavily while she pushed Kuro away from her slightly.

"That's enough right?" Illya asked between heavy pants, as she desperately tried to get her breath back.

"For now, I guess," Kuro simply smiled as she wiped her mouth, before she lay a light kiss on Illya's cheek, causing her sister to blush again.

Illya glared to Kuro slightly, while Kuro just sat relaxed and shrugged her shoulders slightly, "Shouldn't we be getting out now?" Kuro asked as she leaned forward and sighed deeply.

"Kuro, we've only been in here for a little while," Illya pointed out, wondering why Kuro wanted to get out so soon, since she normally stays in right up until the last minute.

"But I'm tired," Kuro groaned as she leaned over the side of the bathtub and looked to Illya with another heavy sigh.

Illya took notice that Kuro really did seem weak and clearly in need of more Mana, but she had just given her some, how could she need more so soon?

"You're probably just dizzy from the heat of the bath water, come on," Illya stated as she wrapped one of Kuro's arms around her shoulders and slowly helped her to her feet, then carefully guided her out of the bathtub. Soon helping her to get dressed and taking her into her bedroom once she drained all the water out of the bathtub, and had turned the bathroom light off.

….

What's wrong with Kuro?" Ruby asked as the magical wand had jumped to attention once she had seen her master enter the bedroom.

"I'm guessing that the bath water was too hot for her, or something," Illya stated as she sat Kuro down on her bed and looked to her with a worried expression, "You okay now?" she asked.

Kuro nodded slightly as she sighed again and breathed deeply, feeling like all her energy was leaving her body, "I'm probably just tired like you said, right?" Kuro smiled to Illya as her whole body shook slightly.

"Yeah….right," Illy replied as she wondered if Kuro was really going to be okay, right now she looked close to passing out, as she was sitting hunched over on the bed, while she ran a hand through her long pink hair.

' _To be honest I am tired, but it's not because I feel dizzy or anything, it's because right now I still need more Mana. This is bad, I don't understand Illya replenished my Mana only a few minutes ago, I shouldn't need more just yet, but somehow I feel so weak right now,'_ Kuro thought before she decided to just go to bed, she knew she needed Mana right now, but she didn't want to bother Illya by keep asking her for more, however she knew it would all catch up with her if she didn't do anything about it soon.

…...

Later on into the night, Kuro found that no matter what she tried she just couldn't get to sleep, she needed Mana right now as she could feel all of her energy slowly leaving her weak body. She couldn't bare it any longer, and she most certainly didn't want to disappear. So she soon crawled off of the big double-bed that her and her Mother shared, and slowly dragged herself to Illya's bedroom, hoping that she was already in a deep sleep so that she could just simply take what she needed, and then leave without Illya even noticing.

Kuro tiptoed across the upstairs hallway and slowly opened the door to Illya's bedroom, being sure to make little to no sound at all. She carefully closed the door behind her and jumped a little when she heard Illya mumble something in her sleep as she rolled over on her bed.

Kuro sighed in relief, glad that she hadn't woken Illya up yet, she looked around the room and took note to the fact that Ruby was lay on the bedside table, seeming to be asleep (although she wasn't sure if magical wands could sleep), she was kinda glad that she hadn't been noticed by the wand yet either.

She then slowly walked upto Illya's bed and sat on the edge of it, she looked to her sleeping sister, and focused on her soft looking, pink lips, swallowing slowly as she watched the other girl's chest rise and fall in time with her slow breaths.

' _Come on, just kiss her, replenish your Mana, then leave and head back to bed without her noticing and waking up, it doesn't sound that hard right?'_ Kuro sighed as she built up all her courage.

Kuro leaned over Illya as she wanted to quickly get this over and done with, so that she could just go back to bed and hopefully get some sleep, _'I really hope Illya's a heavy sleeper,'_

She was now an inch away from her sister's lips, when she heard Illya whisper out something and immediately froze up.

"Kuro?"

She pulled away a little and looked to Illya's eyes, hoping that she hadn't woken her up, and luckily she hadn't as Illya just rolled back over in her sleep and sighed slightly. She was probably just talking her sleep or something, _'Although why did she say my name?'_ Kuro questioned before she shook her head,

' _Never mind that now, just get this over with already,'_ Kuro tried again as she leaned down to Illya and stopped just as her lips brushed lightly against Illya's. She sighed deeply and pulled away again, _'I can't do this,'_ she thought, before she looked to Illya and watched her lips form into a small smile while she slept peacefully.

Kuro ran a hand through her long hair, before she rested a hand on her sister's shoulder and shook her slightly, "Illya, Illya wake up,"

Illya stirred awake as she heard the familiar voice of her sister calling to her in a whispered tone, while she could feel a hand shaking her shoulder slightly. She blinked a few times and then slowly sat up in her bed and looked to the person who had woken her up, "What's wrong Kuro, can't you sleep or something?" she asked as she yawned a little and looked to her sister with tired eyes.

"No, I need Mana," Kuro answered bluntly.

"Really again? But I already gave you some after we came home from shopping with Mama, plus I also provided you with some in the bath before. You shouldn't need any for a while yet, right?" Illya questioned, looking a little confused as to why Kuro needed more Mana so soon.

"Well…." Kuro paused as she hung her head low and sighed deeply.

"Kuro?" Illya seemed a little concerned for her sister as she noticed how her breaths were coming out in heavy pants, and the fact that her body was shaking slightly, _'Maybe she really does need more Mana,'_

"I'm not sure what's going on with me Illya, you're right I shouldn't need any more Mana just yet, but I can just feel all of the energy running out of me, I don't understand this at all," Kuro explained while she kept her eyes focused on the bedsheets.

"I-I don't want to keep bothering you by asking for more again, but…..but I…I…." she trailed off as she clenched the bedsheets in her fists tightly and bit her lip.

"Kuro," Illya slowly lifted up Kuro's head so that she could look at her properly, but was then surprised to see tears streaming down her sister's cheeks, while slight sobs escaped her lips, "Hey why are you crying all of a sudden? If you need Mana, I'll give it to you, I was just wondering why you needed it so soon as all. It's not really a bother to me at all," Illya reassured Kuro as she stroked her cheek and wiped away her tears, _'It's more or less just embarrassing really,'_ Illya thought.

Kuro hid her bright eyes behind her long hair as she bit back her tears, "Hey come here," Illya comforted her sister as she brought her into a warm hug. This side to Kuro was completely new to her, in fact this was the first time she had seen Kuro cry since she almost disappeared forever, that day when Illya's family took her in as one of their own. Illya really wasn't sure how she was meant to comfort her crying little sister like all big sisters are supposed to, but there was a clear sign that she needed Mana right now, while she sat in her sister's arms, still shaking and crying a little, but seeming to be a little calmer now.

"You okay now?" Illya asked as she looked to her sister.

Kuro just nodded slowly as she wiped her tear-filled eyes, before she sat up on her knees and looked Illya in the eyes, cupping her cheeks with both hands.

"Kuro-

Illya was cut off as Kuro closed the small gap between them and kissed Illya's lips deeply. Illya was a little surprised at first since Kuro had caught her off guard, but she soon blushed and relaxed as she melted into the kiss, closing her eyes and giving out a pleasant moan once she felt Kuro's tongue slip into her mouth.

Saliva was soon starting to run down both the girls' chins as Kuro's tongue played with Illya's and she was soon sucking on it. Illya trembled slightly as the deep kiss made her head spin and her heart pound loudly in her chest.

Illya didn't notice at first but Kuro had been slowly unbuttoning her night-shirt, only realising what her sister was doing when the last button was un-done and Kuro slipped the night-shirt off of Illya's shoulders leaving her topless. Illya blushed deeply as she broke the deep kiss and turned away from Kuro slightly, shivering a little when she felt Kuro lay a light kiss on her neck.

"K-Kuro…..you never normally go further than kissing, so why are you taking my top off?" Illya asked as she let Kuro slip her arms out of the sleeves, and then covered her now exposed small chest.

"Because kissing isn't working, I still feel so, so weak, just kissing isn't enough," Kuro explained simply as she sat back and threw Illya's discarded night-shirt to the bedroom floor, before she lay another light kiss on Illya's neck.

Illya sighed deeply, "Fine, but just for tonight, okay?"

Kuro didn't answer as she just wrapped one arm around Illya's bare waist and rested her other hand over Illya's arm. Illya didn't resist Kuro as she let her uncover her small chest, and placed her arms back down to her sides with the dark-skinned girl's hand still resting on top of the left one. Illya shut her eyes tight and moaned slightly when she felt Kuro's hot tongue run over her right perky nub, circle it once or twice, before taking it in her mouth and sucking on it hard.

"Mmmm…..not so hard, K-Kuro," Illya whispered out as she tried to hold back her moans and bit her lip. Kuro took care to not leave any marks as she now started to lick Illya's right hardened nub gently.

' _Every place Kuro kisses or licks tingles, but I can't stop her, she needs this right? She's told me about the other ways of transferring Mana besides just kissing, and although I don't really want to think about doing those things with her, I don't want her to disappear either. It's just for tonight after this she shouldn't need any more for a good amount of time, yeah that's it just let her have her fill tonight, and then I won't have to worry about giving her more soon,'_ Illya thought to herself as she panted a little and could feel Kuro applying the same treatment to her left hardened nub as she had done to her right one.

' _My body feels hot and sweaty and I can't help but tremble every time Kuro licks or kisses me, I know she needs this and all, but she's making my mind go blank right now, and I hate to say it but….'_ Illya fidgeted uncomfortably as she could feel a moist sensation dampening the area between her thighs, _'She's making me wet,'_

Kuro soon stopped her assault on Illya's small breasts as she moved the bedcovers away from them, and pushed Illya to lie back down on her bed, kissing her lips again, and causing Illya to moan slightly.

Kuro still felt weak, very weak, something was wrong her Mana wasn't getting replenished, she just kept getting more and more out of breath, Kuro would have never have thought of going so far with Illya in order to just get Mana from her, but as seconds passed she could feel all her energy drain out of her.

Their lips parted, and while Illya got her breath back, Kuro moved her hands to her sister's pyjama pants, carefully sliding them down slowly. Realising what Kuro was doing Illya instantly stopped her from advancing, as she held her sister's hands tightly and shook her head.

"You're going even further Kuro?" Illya asked as tears filled her eyes, and she felt like pushing Kuro off of her.

Kuro looked back to her with a blank stare, before she simply just nodded.

"Why?" Illya had a really bad feeling about this, just how far was Kuro planning to go, and for what reason, did she really need Mana this badly?

Kuro looked to her sister with glazed over eyes for a moment as she slowly pulled herself away from Illya, allowing her to sit up again, before she removed her hands from Illya's pyjama pants, and took off her own pink vest-top that she had been wearing for bed, leaving her in just her light purple panties now, while she sat on the bed and sighed heavily.

Illya was a little confused as to what Kuro was going to do as her hand was suddenly grabbed, and then placed to rest over Kuro's left breast. Illya was still quite puzzled as to what Kuro was doing right now, until she noticed something and her eyes widened a little.

Illya's hand was now resting over where Kuro's heart was located, and something felt very off there, Kuro's breaths were heavy and spaced out, and her heartbeat was dangerously slow, she was still shaking (although slightly more-so) and it was almost as if Kuro hadn't had any Mana provided to her at all. It was clear that she was still in desperate need for more.

"That's why," Kuro stated as she looked to Illya with a stern look in her eyes.

Illya gazed into Kuro's eyes as she could feel her tears fall, while they ran down her cheeks and she blushed a little when Kuro reached her free hand up and wiped them all away, soon leaning in closer as she lay a soft kiss on her sister's forehead.

Illya had been too lost in Kuro's eyes to notice that she had unconsciously started to move her hand, she didn't know it but she was massaging Kuro's left breast, only snapping back to her senses and realising what she was doing when Kuro gave out a small moan.

' _Did Kuro just…moan? I've never heard her voice sound like that before, she sometimes gasps when we're kissing but I think that's just her trying to get her breath back, I'm normally the only one that moans.'_ Illya looked to where her hand was, and felt like removing it, but Kuro's hand kept it in place.

Illya looked to Kuro, wondering why she was stopping her from removing her hand, her eyes widening a little as Kuro panted and moaned more, looking back to her with pleading eyes, _'Is she enjoying this? Does she actually want me to keep touching her like this?'_ Illya wondered before she moved her hand more and caressed Kuro's breast with each finger, while running her finger-tips over her sister's hardened nub, gaining another slight moan from her.

' _Her nipple is really hard, but thanks to what she did earlier, mine are probably the same right now, her breasts are slightly bigger than mine, but I can tell by her moans that they're just as sensitive.'_ Illya watched Kuro for a reaction as the small voice she was letting out was slowly starting to get louder.

' _She's blushing, her voice sounds….cute, the little whimpers and moans that escape her lips sound so innocent and shy, nothing like the Kuro I'm used to. I may not like this but I want her to stay here with me more than anything right now, she needs this,'_ Illya sighed as she leaned closer to Kuro and kissed her cheek lightly.

"Mmmm…Illya…" Kuro moaned a little louder as Illya pinched her hardened nub, and smiled to her.

"You can continue now," Illya whispered into Kuro's ear, before she removed her hand from her sister's small chest and lay back down on her bed.

"You sure?" Kuro asked as she looked to Illya and blushed slightly.

Illya just nodded with a smile to Kuro in reply, before she took a deep breath and allowed Kuro to remove her pyjama pants and slip her fairly wet underwear off, leaving her now laying completely naked on her bed.

Kuro crouched in-front of Illya's fairly wet entrance and couldn't help but smirk at the clear scent of arousal coming from it. Illya clenched her bedsheets tightly in both fists, preparing herself for what was to come.

' _I never imagined giving my first time away at such a young age, and the thought of giving it to a girl of the same age as me, much less Kuro, (who's meant to be my little sister), but it's not like anyone ever needs to know about this right? It could just stay as a secret between Kuro and me, she needs Mana and I'm providing it for her, that's all this is, nothing more. We aren't 'making love' or anything like that, this isn't even sex really, and we're only doing this in order to keep Kuro alive and well. So just for tonight, I'll let her have her way with my body,'_ Illya decided as she made sure that what happened between her and Kuro tonight would just be another Mana transfer.

"AH!" Illya cried out slightly as she felt Kuro's hot tongue run over her most precious place that had never-before been touched until now, letting out another moan as Kuro gave her aroused slit a long slow lick.

"Ahh….Kuro," Illya bit her bottom lip as she clenched the bedsheets tighter, squirming slightly as Kuro advanced on her more and more.

"AHH! Kuro…..AH!" Illya's whole body trembled as every lick of Kuro's skilled tongue sent shocks of desire, pleasure and passion through her nerves, causing her to breathe heavily and twitch slightly.

"AHHH! Kuro…..no, AHHHH!" Illya threw her head back on her pillow as a feeling of sheer pleasure ran through her body, while Kuro suckled on her slit and lapped up all the juices that flowed out of her now soaked sex.

Kuro sighed as she stopped for a moment and pulled away from Illya's drenched entrance, while she frowned to her sister slightly and licked her lips, while Illya panted heavily and looked to Kuro as slight tears filled her eyes again, threating to fall and stream down her cheeks.

"Why'd you stop?" Illya asked as she caught her breath and sighed deeply, while looking to Kuro with a blush staining her cheeks.

"You're being too loud, someone's going to hear you if you moan that loudly," Kuro simply stated as she traced a finger over each and every delicate fold of Illya's soaked sex, while she smiled at the way her sister's body would tremble because of her light touches.

"W-well how am I supposed to stay quiet when you're licking and sucking down there?" Illya asked as she glared to Kuro slightly and let out a small 'eep' as Kuro slowly dipped her finger inside of her sister, before slipping it back out again.

"Cover your mouth," Kuro simply replied as she tucked a few locks of hair behind her ear, and winked to Illya, before she went back to pleasuring her sister with her tongue, licking her soaked slit, and running the tip of her tongue over her slightly swollen clit every so often.

"AHH! Kuro….Mmm!" Illya covered her lips with one hand, biting her lip as she tried to keep her moans quiet, while she could soon feel Kuro licking her clit over and over again, causing her to squirm and shiver against her sister's touch.

' _I can feel her tongue constantly running over my clit, she's making it harder for me to conceal my moans, and if she keeps going like this…..I….I…'_

"Kuro…no….no more, AHHH!" Illya uncovered her lips for a moment as she moaned at the feeling of Kuro now sucking on her swollen clit, while she stroked her slit with two fingers.

"AHH! S-stop sucking…..I'm scared, I can feel something building up in my stomach…..it feels like I'm going to pee," Illya looked to Kuro with a worried expression, never having known what an orgasm feels like before now.

' _My breath is getting hitched in my throat, something's building up in my lower abdomen, my minds going blank, and I can't hold back my voice anymore, what's happening to me right now'_ Illya wondered as she looked to Kuro for a minute, begging her to stop for a bit and let her calm down.

"Silly Illya, that just means you're close," Kuro smiled as she looked back to Illya and stopped for a second, before she decided to leave Illya's clit alone and went back to pleasuring her now overflowing sex with her tongue.

' _Close? What does she mean by that?'_ Illya didn't really have much time to try and understand what was going on with her as Kuro soon slipped her tongue inside her and started to thrust it deep into her entrance.

"AHHH! K-Kuro…..your tongue…" Illya trembled all over as she shut her eyes tight and rested her hand on top of Kuro's head, tugging on her long pink hair a little. _'It went inside, and I can feel it thrusting in and out of me…..I'm not sure how much more of this I can take,'_

"I-it's deep….AHHH!" she cried out as Kuro's thrusts became faster and faster with every loud moan that Illya let escape her lips, trying to keep herself quiet wasn't an option anymore, as she was quickly reaching her limit.

' _I have to stop her…..she's making me go crazy right now, but it feels…so good, I've never felt anything like this before,'_ Illya thought as she tugged harder on Kuro's hair and felt like screaming.

"K-Kuro…..s-stop! I can't….I can't…..no more," Illya whispered out between moans, as she felt her pleasure hitting its highest peak.

Kuro paused for a second as she pulled away from Illya's sex and smiled to her, "Its okay Illya, just come," she stated as she looked Illya in the eye.

Illya looked back to Kuro, gazing into her bright eyes, blushing deeply and loosening her tight grip on her long hair for a moment, before she swallowed slowly and nodded to her sister. Kuro then slipped her tongue inside Illya again, thrusting deep into her, wanting to quickly drive her over the edge.

"Kuro….Kuro….Ahh…..AHH!" Illya moaned between heavy, spaced-out pants as she was now certain that she couldn't hold back any longer.

' _My body feels like it's on fire, my mind's gone completely blank, and I'm finding it hard to catch my breath….I feel like I'm going to burst,'_ Illya clenched her teeth together as she tugged on Kuro's hair again and gasped, reaching her limit.

"K-Kuro…Ahh….Ahhh…..YAAAAAHHHHHHHH!"

Illya let out a loud scream of release as she felt sheer ecstasy ripple through her whole body, her eyes shut tight, tears run down her cheeks, her toes curled, she clenched the bedsheets in one hand tightly, making her knuckles turn white, and almost pulled Kuro's long hair out with how much she was tugging at it with her other hand right now, while her whole body spasmed and she rolled her hips against Kuro's deep and fast thrusts.

Kuro not letting up for a single second, causing Illya to ride out the intense waves of her first climax, while Kuro lapped up all of her sister's juices, being sure to not let a single drop miss her lips, only stopping slightly when Illya's climax finally ended and she started to slowly calm down.

"I-is that….enough now?" Illya panted heavily as she struggled to get her breath back, opening her eyes and looking to Kuro through a slightly blurred vision. She moaned a little and squirmed at the feel of Kuro licking her clean, before she sat back up on her the bed and covered her lips with two fingers, while she swallowed all that she had taken from her sister, smiling to Illya as she licked her lips.

"You came a lot, so it should last me a good amount of time," Kuro stated as she sighed slightly, finally feeling full of energy once again, "I don't feel weak anymore, and I can tell that my Mana is now fully replenished,"

"Good," Illya nodded as she slowly sat up and was now able to catch her breath and breathe properly again, while she sighed slightly and guessed that Kuro would go back to her regular-self and start teasing her or something, but instead she was surprised when Kuro moved closer to her and embraced her tightly.

"Kuro?" Illya questioned as she sat relaxed in Kuro's arms and looked to her, seeming a little taken back as to Kuro suddenly hugging her like this.

"Sorry I took your first time, Illya," Kuro genuinely sounded like she regretted what she had just done to Illya, and it was clear that she meant that she was sorry for all of this. Illya sat looking confused in her sister's arms for a moment, before she just smiled and hugged Kuro back.

"It's alright, you needed Mana right?"

"What do you mean?" Kuro asked as she pulled away from Illya slightly and was a little surprised that she wasn't mad or upset right now.

"It was clear that you were in a desperate need for Mana, and so I simply provided you with some, that's all this was. Let's not call it 'Sex', and instead let's just say I was taking care of my little sister like all big sisters are meant to okay?" Illya stated with a smile to Kuro as she stroked her cheek lightly.

Kuro looked to Illya taken aback for a few moments, surprised at how well she was talking all of this, before she smiled back to her sister, "Thank you, Illya," she lightly kissed Illya on her forehead, while Illya blushed slightly and closed her eyes for a second, opening them again as she felt Kuro's hand stroke her cheek softly.

Kuro let go of Illya as she lay back down on her bed, resting her head on her pillow as she sighed deeply.

"You tired now?" Kuro asked as she smiled to Illya and leaned forward, brushing her long, silver hair out of her eyes.

Illya just nodded in reply as she looked to Kuro with tired eyes that were now only half-open, letting out a slow breath as she looked over Kuro's sweating body, and was glad to see that she wasn't shaking any longer.

"Alright then, goodnight," Kuro stated as she crawled off of the bed and reached down to pick up her forgotten vest-top, but stopped when she heard Illya's voice call to her.

"Wait, Kuro!" Illya sat up in her bed again as she crawled to the edge of her bed and tugged on Kuro's panties, getting her attention in the process.

"What is it?" Kuro asked as she stood back up straight and looked back to Illya, leaving her vest-top still laying on the bedroom floor.

Illya looked to Kuro for a minute, getting lost in her bright eyes again, before she blushed deeply and turned away from her slightly, "Don't go," she whispered out as she looked to the bedsheets nervously.

Kuro looked to Illya with a wondering expression, before she smiled and crawled back onto the bed, lifting her sister's head to look back at her again, "Okay I'll stay tonight and keep my little sister company," she stated as she covered both her and Illya with the bedcovers.

"That's not what I meant, and stop calling yourself the 'Big sister," Illya glared to Kuro as she let go of her.

"Well I think what I just did to you was way more 'Adult' than probably anything you've done, right?" Kuro smiled as she winked to Illya.

"I told you that just another Mana transfer, and nothing more,"

"Okay, and you didn't enjoy it one little bit, right?" Kuro folded her arms.

"That's right, I didn't enjoy it at all!" Illya nodded as her voice had an angered tone to it now.

Kuro smirked as she leaned in close to Illya and kissed her cheek lightly, "You're lying,"

Illya blushed as she mumbled something under her breath and turned away from Kuro, "Just go to sleep already," she replied as she lay down and turned her back to her sister, while Kuro smiled and settled down into the bed as well.

' _She definitely has enough Mana now, she's back to her regular-self,'_ Illya thought as she sighed slightly and relaxed under the warm covers of her bed, rolling over to face Kuro again as she felt a little cold since she was still completely naked.

Kuro smiled as she wrapped an arm around Illya's waist and pulled her closer to her chest, while Illya snuggled up close to her and nuzzled into her neck slightly, "Goodnight Kuro," she whispered with a small smile.

"Night Illya," Kuro replied as she kissed Illya's forehead lightly and combed her free hand through her long, silver, un-tidy hair.

And soon the two young girls drifted off into a peaceful sleep together.

….

It was late in the morning when Illya stirred awake in her bed, and blinked a few times, her eyes getting used to the bright sunshine that was peeking through the slightly open curtains from the bedroom window. She slowly sat up and yawned as she rubbed her tired eyes, and was almost instantly greeted by her trusty magical wand, Ruby.

"Good morning Illya, I suspect you slept well last night?" Ruby asked cheerfully as she chuckled at the state that Illya was I right now.

"What are you talking about Ruby?" Illya asked, still feeling half-asleep. Ruby pointed to something lying beside Illya, and as Illya looked to where her wand was pointing she saw Kuro laying in her bed, fast asleep.

"Oh yeah, that's right I let Kuro stay over in my bed last night after I gave her some Mana," Illya thought out loud as she remembered just what had happened between her and Kuro last night.

"It sounded like you were giving her more than just Mana by the volume of your screams last night Illya," Ruby joked with another chuckle.

"Kissing wasn't working so I let her go a little further-

"A little?" Ruby cut Illya off as she remembered hearing her master's loud screams and moans of pleasure last night, while she was trying to sleep still.

"Okay, a lot, but only because she needed it," Illya stated with an annoyed tone in her voice.

"Right, right," Ruby replied as she nodded to her master.

Illya sighed deeply as she looked to Kuro's sleeping body, she was still sweating a little from last night, but at least she wasn't still shaking and she seemed to be relaxed, so by Illya's guess she still had enough Mana, and wouldn't need any more when she woke up.

She was topless and although Illya remembered being in Kuro's arms when she fell asleep, it seemed that Kuro had rolled over during the night as she was now laying with her back to Illya, and she was curled up in the fetal position, probably trying to keep herself warm.

Illya smiled slightly as she heard Kuro sigh in her sleep, while she watched her chest rise and fall slowly to the steady rhythm of her breathing, _'Looks like she won't be needing any Mana from me for a while,'_ she thought with a smile, glad that Kuro's Mana hadn't decreased and all been consumed during the night.

' _Although I wonder why did she keep needing more Mana last night? I mean it even got to the point where the only thing that worked was letting her 'go down' on me,'_ Illya wondered as she tried to think for a moment, _'Hmm….she started acting weird once we had gotten out of the bath right? She got dizzy and went to bed, and then later came into my room and woke me up asking for Mana. Hmmm…..maybe there was something in that lotion that I used last night, and maybe it affected her somehow,'_

Illya decided to leave Kuro sleeping, as she quickly got out of her bed and put her forgotten pyjamas and underwear from last night into a basket ready to be washed, before getting dressed into causal clothing and made her way to the bathroom, along with Ruby following her.

Once in the bathroom Illya picked up the bottle of new lotion that she had used as bubble bath last night, turning it over to read the ingredients that it contained,

' _Alright let's see what's in this, hmm…..water, natural oils, glycerin whatever that is, citric acid, scents, anti-microbials, a bunch of other stuff, umm….moisturizing gel and thermal spring water,'_ Illya read through the ingredients, not really taking much notice to any of them until she read out the last one in her head a few times.

"Hmm….thermal spring water? Where have I heard that before?" she wondered out-loud as she thought for a moment.

"Isn't that another way of saying, 'Hot spring water'?" Ruby asked as she read all the ingredients over Illya's shoulder and heard her asking herself about the last one.

Illya's eyes widened at that as she remembered what Kuro had said last night once she got into the bathtub, "THAT'S IT!" she said in a raised voice and gave Ruby a fright.

"What's it?" Ruby asked, seeming confused now.

"No wonder Kuro said that the water felt like a hot spring, because that's what was intended. The thermal spring water was added in to make it feel like you really were in a hot spring, but it must have contained the same thing un-natural man-made hot springs have in them. Now it all makes sense Kuro kept needing more Mana last night because the chemicals that are used in that water to give it a heavily effect causes Kuro's Mana to be consumed much quicker than normal. And I guess Kissing wasn't working because maybe the effect hadn't wore off completely yet, so Kuro's Mana was still be consumed quicker, so it took going as far as letting her 'go down' on me in order for her to finally have her Mana fully replenished," Illya explained, now finally realising what the reason for what happened last night with Kuro was.

"So it was all because she had a bath in that lotion?" Ruby asked, seeming to understand most of what Illya had said.

"I guess so, afterwards she seemed back to her normal-self, and she seemed to be sleeping fine this morning, so I'm guessing that the effects of what was in the lotion must have worn off during the night somewhere," Illya explained as she nodded to her wand.

' _So really I caused her Mana to decrease so much, I mean considering the fact I brought the lotion, and then used it as bubble bath, I guess I got to pay for my stupid mistake by letting Kuro have her way with my body last night,'_ Illya thought as she now realised that what happened between her and Kuro could have been easily avoided if she had just taken more notice to what ingredients were inside the lotion she had brought and used.

' _Argh! Stupid, Stupid, STUPID ILLYA!'_ Illya slapped herself in the head mentally for being so foolish and making such a mistake.

"I guess buying and then using that fancy lotion kinda backfired on you then huh?" Ruby chuckled nervously, while Illya went silent for a moment, before she looked to Ruby again.

"R-Ruby, I let Kuro have my first time last night," Illya stated as she spoke in a whispered tone and had the expression of sheer worry on her face.

Ruby nodded slowly, wondering if Illya was okay as she looked like she was really anxious about something now.

' _I let Kuro do so many things to me last night, I let her kiss me, play with my breasts, undress me, I let her 'go down' on me, I let her make me moan and scream out her name and I let her make me come, heck I even touched her breast and made her moan at one point. I said it was nothing more than just another Mana transfer, but I can't deny what really happened between us last night, we had 'Sex','_ Illya was quickly going into a panicked state at the fact that last night was really her doing, and Kuro had just been dragged into it all because she simply needed Mana.

' _This morning I had woken up completely naked, soaked in my own sweat, my hair a mess, my heart still racing slightly, and I could still feel my cheeks heating up, and I could've prevented it all? No way last night wasn't real sex, it was nothing more than another Mana transfer, right?'_ Illya quickly walked back to her bedroom, trying to make all of her memories of the events that had taken place last night go away, shaking her head franticly.

' _Kuro and I didn't have sex, it was just a Mana transfer, and nothing more, it wasn't sex, it wasn't, it wasn't!'_ Illya repeated over and over again in her head, trying to convince herself that what she was saying was actually true, while Ruby seemed to be a little worried for her master now.

"Ruby," Illya turned back to her wand.

"Yes?" Ruby was now quite concerned for her master since she seemed to be in a panicked state right now.

"Kuro and I, we…we did so many dirty and perverted things last night, but it was just for Mana right? Please tell me it wasn't sex!" Illya begged as tears welled up in her eyes.

"Well…..I umm…." Ruby wasn't too sure how exactly to calm her master down, while she appeared to be in such a distressed state. She was about to say something, when they both heard a voice call to them.

"Illya, you're noisy, I'm still tried," Kuro groaned as she was now sitting up in Illya's bed, rubbing her tired eyes and looked to her sister.

Illya and Ruby looked to Kuro, as Illya quickly came and sat beside her on the bed, while Ruby sighed slightly and flew to rest on Illya's bedside table.

"Kuro, we didn't have sex last night, right?" Illya asked, still sounding incredibly stressed out.

"You said it was nothing but a Mana transfer last night, that's what we agreed on right?" Kuro asked as she looked to Illya and stretched slightly, not really understanding what Illya was getting so worked up over.

Illya and Ruby sighed heavily in relief that Kuro had said exactly what Illya had wanted (and kinda needed) her to say. "Thank you Kuro, you don't know how relieved I am to hear you say that and calm Illya down," Ruby said, while Kuro seemed confused and looked to her sister for some sort of explanation as to what had been going on while she had been asleep.

"Huh, what do you mean?" Kuro asked.

"It doesn't matter Kuro," Ruby stated.

Kuro still seemed confused and a little spectacle about how the magical wand was acting towards her, but decided to not let it bother her, as Illya caught her attention by resting a hand on her bare shoulder.

"Listen Kuro, there's something I need to tell you," Illya stated nervously.

"Okay, what is it?"

"Last night was kinda my fault,"

"What do you mean?" Kuro asked as she seemed confused and didn't quite understand what Illya was telling her.

"Well you see that lotion that I brought and then used had thermal spring water added into it," Illya confessed with a sigh.

"So?" Kuro still looked completely confused as to what Illya was trying to tell her, obviously not really knowing where Illya was going with what she was saying right now.

' _I'm going to have to just spell it out for her, aren't I?'_ Illya thought before she went onto explain in more detail, and see if Kuro would understand.

"Thermal spring water is another way of saying, 'Hot spring' water, so when you said that the water felt like a hot spring to you, you were completely right, however-

"My Mana decreases to an incredible speed that's much faster than normal because of the chemicals that are added into an un-natural hot spring. So that must be why I kept needing more Mana last night," Kuro cut Illya off as she caught on and finished her explanation for her.

"Yes, exactly, and I guess Kissing wasn't working because the effects of the lotion hadn't worn off just yet, so your Mana was still being consumed faster than normal," Illya added with a relieved smile to Kuro.

"It was my fault for not looking to see what was in that lotion, I'm sorry Kuro, if it weren't for my mistake last night wouldn't have happened, and you wouldn't have had to go through feeling like you were going to disappear again," Illya hung her head low as she apologized and sighed heavily.

"It's alright, I was sacred yes, but it's not like you planned it right?" Kuro asked with a smile to her sister.

"No, no I would never want you to disappear, I swear," Illya immediately lifted her head and shook it frantically, never really wanting to know what her life would be like without Kuro there with her.

"Then it's fine," Kuro stated with a nod as she patted Illya on top of her head and caused her to blush slightly.

"Just don't use that lotion in future alright?" Illya asked in a low tone.

"Got it," Kuro replied, before she got an idea and smirked to her sister, "Unless, you want me to use it,"

"What, of course not, why would I ever want you to use something like that, and risk you disappearing forever?" Illya looked confused now as she tilted her head slightly while looking to Kuro.

"Well if you planned it all out to make it seem like an accident then that would make sense right?"

"Why would I plan something like that out?"

"So my Mana would decrease and I would have to 'go down' on you in order to replenish it," Kuro explained with a smirk as she threw the covers of Illya's bed off of her and stood up from the bed, reaching down to pick up her vest-top that she had taken off last night.

"Hey, last night was just a one-time thing, I would never let you do those kind of things to me again," Illya stated while she looked to Kuro with a annoyed expression on her face, while Kuro just slipped on her vest-top and smiled to her sister.

"Not even if I really needed it?"

Illya paused for a moment as she looked to Kuro's smiling face, and sighed slightly, "I guess if it was really an emergency, then I'd let you do it again, but only if you were really in desperate need of Mana like you were last night," she stated nervously.

"Well it's no surprise that you would let me do those things to you again, after all you did keep moaning and screaming out my name last night," Kuro rested her hands on her hips as she loved poking fun at her sister like this.

"I was only doing that because you kept licking and sucking me down there, I kept telling you to stop, but you didn't!" Illya's voice was slightly raised as she was becoming more and more annoyed with her sister while Kuro just kept pushing her.

"You're being too loud Illya, someone's going to hear you if you're not careful," Kuro pointed out while Illya glared to her.

"You're the one that started this," Illya mumbled under her breath as she lowered her voice and turned away from Kuro a little.

Kuro smiled as she leaned down to Illya as she cupped her cheek and brought her face back to look at her, before she surprised her with a deep kiss. Illya's eyes widened slightly at the sudden kiss, but soon closed as she melted into the kiss when she felt Kuro slip her tongue in. Kuro sighed with a smile as their lips parted and she stroked her sister's cheek.

"Why'd you do that, you don't need any Mana after last night right?" Illya asked now seeming much more calm, but was still blushing and glaring to her sister slightly.

"To calm you down a little," Kuro simply replied as she kissed Illya on her forehead.

"You're the one that got me riled up in the first place,"

"Anyway, shall we go for a shower?" Kuro asked, changing the subject.

"Why?" Illya asked deciding to just drop the previous subject.

"Illya, we're both soaked in sweat and I can still smell the scent of arousal on you from last night, I don't think we can really go downstairs like this," Kuro explained.

"Right, I guess having a shower would be smart," Illya nodded as she blushed at remembered that they were both still soaked in sweat and looked kind of worse-for-wear after last night.

"But keep your hands to yourself alright," Illya warned Kuro as she got off the bed and Kuro just nodded to her, while Ruby was still resting on Illya's bedside table, as she sighed slightly at the two young girls, now back to their regular-selves.

….

"Ahh so you two finally decided to come downstairs then?" Shirou asked as he stood in the kitchen with Sella, helping to prepare breakfast for everyone.

"Good morning Onii-chan, I trust you slept well last night?" Kuro smiled as she greeted Shirou happily putting on her 'innocent act', while Illya was still glaring to her sister slightly.

"Just what were you two auguring about up there?" Sella asked saying that they all had obviously heard the two young girls yelling at each other this morning.

"Well-

"Kuro got lonely last night without Mama, so I woke up to find her sleeping in my bed this morning, I didn't mind all that much, but she could have just asked me to keep her company during the night, instead of sneaking into my bed," Illya explained, while she cut Kuro off and elbowed her in her side.

"Well it was surprising that your Mother took off so quickly after dinner last night, but she should be back soon, so you shouldn't have to worry about being lonely again Kuro," Sella stated with a smile to Kuro.

"I wasn't lonely-

Illya elbowed her again.

"Quit doing that!" Kuro glared to Illya as she rubbed her wounded side and looked about ready to punch her sister.

"Alright then you two sit down and have some breakfast before it gets cold," Shirou said with a smile to the two sisters.

"Okay," Kuro smiled as she happily went to go and sit at the table acting all innocent again, before she was stopped by Illya tugging on her top and getting her attention.

Kuro looked back to Illya with a wondering expression, while Illya stood there blushing and looking down at her feet nervously.

"What is it?" Kuro asked.

"What you did to me last night…it stays between us right?" Illya asked in a whispered tone as she looked to Kuro nervously, still blushing a deep red.

Kuro looked to Illya for a moment, before she simply smiled and nodded to her, "My lips are sealed," she replied with a wink.

Illya smiled back to Kuro and thanked her, before the two came and sat down beside each other at the kitchen table.

"You two really are close aren't you?" Shirou asked as he smiled to his two younger sisters.

"What do you mean Onii-chan?" Illya asked, while Kuro happily started talking to Liz, who was sitting across from her at the table.

"Never mind, don't worry about it," Shirou smiled, while Illya just looked to him a little confused, before she glanced to Kuro and smiled slightly with a sigh.

' _I just hope she keeps what happened between her and me last night a secret,'_


End file.
